Apparatus determining static pressures in pumping wells



May 21, 1957 T. w. BELL ETAL APPARATUS DETERMINING STATIC PRESSURES INPUMPING WELLS Filed Nov. 24, 1954 2 Sheets-Sheet 1 u n. um

T. w. BELL ETAL 2,792,709

May 21;,1957

APPARATUS DETERMINING STATIC PRESSURES IN PUMPING WELLS Filed Nov. 24,19454A 2 "snetsfsheet 2 APPARATUS ,DETERMINING STATIC PRESSURES INPUMPING WELLS Thomas W. Bell, Arcadia, and Howard C. Stone, Bakerstield,Calif., assignors to The Texas Company, New York, N. Y., a corporationof Delaware Application November 24, 1954, Serial No. 470,992

2 Claims. (Cl. 73155) This invention relates generally tto pressuremeasurement in pumping wells and particularly Vto an apparatus for[determining subsurface static pressures therein.

When low specific gravity, high viscosity crude oils are encountered inpumping wells, subsurface static pressures must be :obtained usually bythe use of pressure recording equipment. Due to solution gas `containedin heavy crude oil, sonic fluid level tests give unreliable results.

.'lhe :pressure recorder is generally run on the end of a string ot'solid sucker rods, a slow and costly operation, especially when the rodswill not drop freely because of their own weight through the viscouscrude oil.

Accordingly, it is an object of -our invention to provide an improvedapparatus for obtaining subsurface static pressures in pumping wellswhich is economical both in time and cost and yet precise.

lt is another object of our invention to provide an improved apparatusfor `determining bottom hole static pressures where pump-ing of veryviscous crude oil is encountered.

t Still another object of invention is to provide an improved apparatusfor determining bottom hole static pressures which is simple instructure and accurate in performance.

These and other objects and advantages of the present invention will beapparent from the following description of a preferred form of theinvention and from the drawing in which:

Fig. l is a diagrammatic vertical sectional view of a well to which thisinvention has been applied;

Fig. 2 is a typical curve on a chart from a pressure recorder used inour apparatus for the determination of the bottom hole pressure;

Fig. 3 shows in detail the pumping structure end of the diagrammaticdisclosure of Fig. 1; and

Fig. 4 is a partial sectional view of the crossover check valve.

In accordance with one aspect of the present invention, an apparatus fordetermining subsurface static pressure in pumping wells is disclosedwhich permits the measurement thereof by comparison of a balancingpressure of known value with the same.

The manner in which this is accomplished may be understood by referringto the drawings, which, in Fig. 1, discloses a well casing at 10, with acas-inghead therefor at 11 and suitable outlet at 11a. Production tubing12 is located annularly within the casing 10, with a tubing head at 13and outlet therefor at 13a. The tubing head 13 supports a stulng box at14, through which a series or string of hollow sucker rods 15, joinedtogether, extend, leakage therefrom being prevented by the use of asuitable packing material. These sucker rods actuate a lift pump showndiagrammatically at 16, located at the bottom of the production tubingin the vicinity of perforated liner 19a. The pump is joined to thehollow sucker rods by a perforated coupling including some form of checkvalve device 17 to prevent flow of well uid into the `string of hollowsucker rods. Operation of the pump by nited States Patent fice meansLof, the. sucker rod string is effected by conventional oil lieldmethods, including the use of walking beams, etc., andcsince noinvention is considered to be involved in this aspect of .thecombination, details thereof are not disclosed.

Referring specifically to Fig. 3, there islshown a series of hollowsucker `rods 15 joined to each other by means of couplings, one of whichis indicated at 30, the sucker rods having `end .protectors `shown inblock form at 31. The bottom sucker rod is joined to a cross-over checkvalve device 17 at one end thereof, with the other end of the check'valve `device `being joined to a solid sucker Vrod indicated at 32. The.bottom end of this solid sucker rod 32 in turn` is joined `by acoupling 33 to a deep well lift pump 16, which is adapted to be immersedin the well `fluid to bepumped. This well pump is shown inconventionalized form and 4comprises the pump hold down structure at 34,`whichfis adapted to be `placed in locking position with the lock downpump shoe shown at 16a. This pump comprises an outer shell or workingbarrel 35 and a-plunger 36, which contains the traveling valve structureat `37. A standing valve structure at 38 is adjacent the bottom ofJthenlift pump. `Appropriate series of openings in the outer shell andplunger are `disclosed at 39.

The pumping `operation may be described briefly as followsrthe lift pump16 is placed at a depth in the well at which the pump will stay coveredby Huid during the pumping operation. The pumping cycle starts with anupward strokeof the sucker rods 15, which pulls the plunger 36 upthrough theworliing barrel 35. The traveling valve at 37 closes, thestanding valve at 33 in the working barrel opens, and fluid enters theworking barrel from the well. On a downward stroke of the plunger, thetraveling valve opens, the standing valve` closes, and fluid is forcedfrom the working barrel through the plunger into the production tubing12 through the openings 39. Repeated strokes bring the well uid to thesurface through the outlet at 13a, Fig. 2.

IFig. 4 is an enlarged detail of the cross-over check valve device 17.This comprises ends threaded to receive the bottom end of the series ofhollow sucker rods at 40 and the top end of the solid sucker rod 32 at41. The axial bore of the valve device 17 has a valv-e seat at 42 forseating the valve ball 43, which is held in closed or seated position bya bias spring 44, which is adjusted by the spring follower 45, insertedin the end 41 before the solid sucker rod 32 is attached thereto.

The valve device conta-ins perforations which are equally spaced aboutthe circumference, two of which are shown at 46, passing through thewall of the valve device to establish communication with the internalaxial bore.

The top of the string of hollow sucker rods is connected to a highpressure gas supply 18, e. g. compressed nitrogen, by means of the line19, with a high pressure control valve at 20. Manifolded to the gassupply line 19, there is a pressure gage 21, to indicate equilibriumconditions, and pressure recording means at 21a.

During normal pumping operation, the pump is Elocked on the pump shoeindicated at 16a. For subsurface pressure determinations, the pumping issuspended and the pump is raised off the pump shoe, as indicated in Fig.1, to allow the fluid level, shown at WL in the Well casing 10 andproduction tubing 12, to equalize in accordance with the subsurfaceformation pressure. The well is allowed to stand idle so long asconsidered necessary for the static formation pressure to reachequilibrium conditions before determination of the subsurface staticpressure is started.

Then high pressure gas from the supply 18 is injected periodically intothe string of hollow sucker rods 15, until the pressure as indicated bythe pressure gage 21, manifolded to the supply line 19, reachesequilibrium.

This operation unseats the valve ball 43 and displaces any uid which mayhave passed into the hollow sucker rods and is depicted in the chartshown in Fig. 2, where that portion of the curve over area A indicatesthe initial build-up `of the bottom hole pressure, and the portion B,under the curve, indicates the pressure stabilized at the surface with asmall volume of gas liowing down the sucker rods.

High pressure gas is injected momentarily several times into the hollowsucker rods and the pressure allowed to reach equilibrium, `in order toassure that well iiuid, which may have yaccumulated in the string ofhollow sucker rods, is expelled. This action is indicated at portion C,under the curve, which covers the fast build-up of pressure byincreasing the volume of flowing gas from supply 18 and a relativelyfast decline to the stabilized pressure; while portion D, under thecurve, indicates the gradual decline of the pressure due to leaks in theequipment, and the portion E, under the curve, indicates thebleeding-oli pressure decline. The points indicated at X and Y are thepressures used in the calculation of the bottom hole pressures.

The subsurface pressure at a desired level as obtained by the describedprocedure, will be equal to the equilibrium pressure indicated by thepressure gage at 21, Fig. l, plus .the computed pressure head exerted bythe gas column contained within the hollow sucker rods at that level.Data for such a computation are available from the density of the gasused, the known depth of the spring loaded check valve, 17, below thesurface at the desired level, and the pressure recorded by 'the gage at21, Fig. l.

The pressure measured at the surface by gage 21 can be corrected to thepressure at the bottom of the gas column by using Dices formula,expressed as:

P (at rcheck valve 17 )=P (at surface, Y

gage 21) ex where e equals 2.718 and where G is the density of thepressurized gas;

h is the depth of check Valve 17 below the surface, and

t is the average of the temperatures at the surface and at the depth ofthe check valve. The constant 53.3 is the same for all gases.

Experiments have shown that the pressure values obtained by the use ofhollow sucker rods and corrected by this formula are as accurate asthose obtained by running a pressure recorder on solid sucker rods intothe well.

Since certain changes may be made in the above described method andapparatus without departing from the scope of the invention hereininvolved, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not limitative.

We claim: Y

l. An apparatus for determining bottom hole static pressure in a pumpingwell containing low specic gravity,

rhigh viscosity well liuid comprising, in combination,

means for leading off said well fluid extending down into said well,pumping means for lifting said well iiuid through said first mentionedmeans, a plurality of hollow rods connected to each `other within saidrst mentioned means and joined to said pumping means for actuating thesame, means for providing high pressure uid connected to said pluralityof hollow rods, and means coupled into said rods adjacent said pumpingmeans for controlling the flow of said high pressure fluid and said welluid from said plurality of hollow rods and for preventing reverse flowof well fluid thereinto.

2. In an apparatus for measuring the bottom hole static pressure of apumping well containing very viscous fluid,

the combination comprising production tubing, means for References Citedin the tile of this patent UNITED STATES PATENTS Browall June 23, 1942Toth et al. Oct. 17, 1944

